LCE: Systemd two years on

Those "individual components" are subject to the same rules as normal systemd units (e.g. daemons), in that their exit status is recorded and each component, after it finishes, has a status of Success or Failure. Other components have dependency rules, so if they are marked to require the first component, they will not be started if it fails.

If a basic boot-up "component" fails, e.g. fsck of the root filesystem, then the system bootup will be stopped and a login prompt will be opened for the admin to fix things. So in this regard this is similar to sysvinit, except that what is required and what is not for the basic boot is configurable.